Enable native tabs on macOS

atom/browser/native_window_mac.h

@@ -179,6 +179,8 @@ class NativeWindowMac : public NativeWindow,
   // The "titleBarStyle" option.
   TitleBarStyle title_bar_style_;
 
+  std::string tabbing_identifier_;
+
   DISALLOW_COPY_AND_ASSIGN(NativeWindowMac);
 };
 

atom/browser/native_window_mac.mm

@@ -656,7 +656,8 @@ NativeWindowMac::NativeWindowMac(
       was_fullscreen_(false),
       zoom_to_page_width_(false),
       attention_request_id_(0),
-      title_bar_style_(NORMAL) {
+      title_bar_style_(NORMAL),
+      tabbing_identifier_(""){
   int width = 800, height = 600;
   options.Get(options::kWidth, &width);
   options.Get(options::kHeight, &height);
@@ -682,6 +683,8 @@ NativeWindowMac::NativeWindowMac(
 
   options.Get(options::kTitleBarStyle, &title_bar_style_);
 
+  options.Get(options::kTabbingIdentifier, &tabbing_identifier_);
+
   std::string windowType;
   options.Get(options::kType, &windowType);
 
@@ -754,6 +757,16 @@ NativeWindowMac::NativeWindowMac(
     [window_ setOpaque:NO];
   }
 
+  if (base::mac::IsAtLeastOS10_12()) {
+    // Create a tab only if tabbing identifier is specified and window has
+    // a native title bar.
+    if (tabbing_identifier_.empty() || transparent() || !has_frame()) {
+      [window_ setTabbingMode:NSWindowTabbingModeDisallowed];
+    } else {
+      [window_ setTabbingIdentifier:base::SysUTF8ToNSString(tabbing_identifier_)];
+    }
+  }
+
   // We will manage window's lifetime ourselves.
   [window_ setReleasedWhenClosed:NO];
 

atom/common/options_switches.cc

@@ -51,6 +51,9 @@ const char kZoomToPageWidth[] = "zoomToPageWidth";
 // The requested title bar style for the window
 const char kTitleBarStyle[] = "titleBarStyle";
 
+// Tabbing identifier for the window if native tabs are enabled on macOS.
+const char kTabbingIdentifier[] = "tabbingIdentifier";
+
 // The menu bar is hidden unless "Alt" is pressed.
 const char kAutoHideMenuBar[] = "autoHideMenuBar";
 

atom/common/options_switches.h

@@ -36,6 +36,7 @@ extern const char kAcceptFirstMouse[];
 extern const char kUseContentSize[];
 extern const char kZoomToPageWidth[];
 extern const char kTitleBarStyle[];
+extern const char kTabbingIdentifier[];
 extern const char kAutoHideMenuBar[];
 extern const char kEnableLargerThanScreen[];
 extern const char kDarkTheme[];

docs/api/browser-window.md

@@ -264,6 +264,9 @@ It creates a new `BrowserWindow` with native properties as set by the `options`.
       canvas features. Default is `false`.
     * `scrollBounce` Boolean (optional) - Enables scroll bounce (rubber banding) effect on
       macOS. Default is `false`.
+    * `tabbingIdentifier` String (optional) - Tab group name, allows opening the
+       window as a native tab on macOS 10.12+. Windows with the same tabbing identifier will
+       be grouped together.
     * `blinkFeatures` String (optional) - A list of feature strings separated by `,`, like
       `CSSVariables,KeyboardEventKey` to enable. The full list of supported feature
       strings can be found in the [RuntimeEnabledFeatures.json5][blink-feature-string]